Aneurysmal dilatation of the vein of Galen (AVG) is a common finding in vascular malformations that involve the Galenic system and spontaneous thrombosis is very rare. Although the presentation of the cases may differ with the age, the mortality and morbidity is high in all age groups. Here, we present a case of AVG in a six-month-old boy. The patient underwent insertion of a ventriculoperitoneal shunt. Surveillance of the lesion with subsequent MRI revealed spontaneous thrombosis of the AVG with excellent clinical outcome. Proposed mechanisms of spontaneous thrombosis include slow flow shunts, obstruction of the venous outflow or obstruction of the feeding artery. The case is discussed with the relevant literature.